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This five span bridge at Ashcroft replaces a sixty
year old truss structure. The installation of the new 783 foot (233
metre) long bridge posed an erection problem as the Thompson River
becomes a torrent during run off. We chose to launch the steel trapezoidal
bathtub girders from both sides, closing in the middle. The bridge
was launched over a roller system that we designed to minimize the
critical web buckling stresses. The rollers were mounted on rocker
beams which also simplified passage of plate thickness changes.
Somerset designed a falsework bent, an expandable spreader bar lifting
system and a launching nose. An innovative hydraulic push-grip mechanism
was conceived to replace the pulling hoist and reeving operation
which is conventionally used. Later, a scheme to dismantle the old
bridge was engineered and the truss was removed from the centre
back, piece by piece.
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